Volume 16 Supplement 1
Model-based prediction of maximum pool size in the ribbon synapse
© Parmelee et al. 2015
Published: 18 December 2015
Maximum pool size predictions from pulse train data
Estimate for A, from back-extrapolation
Estimate for A, from the model
-10 mV (stronger)
-30 mV (weaker)
We developed a model-based approach to estimate A from the limiting release R. We modeled the rate of release (resp. replenishment) to simply be proportional to the number of vesicles on the ribbon (resp. vacant ribbon sites), and using the measured timescale τr (resp. τa). By solving the alternating differential equations, we derived a recurrence relation for the release during each pulse, Ri, which we then solved to obtain a closed form expression for Ri and the limiting release R. Specifically, we found that A = cR, where c is a function of τr,τa,Δt,T, and p, with p a release constant that captures the stimulus dependence of release probabilities, and can be estimated from the first release, R1. In contrast to the back-extrapolation method, our model-based estimate for A was similar across stimulus types (Table 1), while p was much smaller for the weaker stimulus. This suggests that available pool size does not change with stimulus strength; instead, differences in release result from changes in release probability.
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